All references, including any patents or patent application, cited in this specification are hereby incorporated by reference to enable full understanding of the invention. Nevertheless, such references are not to be read as constituting an admission that any of these documents forms part of the common general knowledge in the art, in Australia or in any other country. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents.
Bone is a living tissue that is constantly being renewed. It contains cells and specialized collagen fibres, encrusted with a crystalline mineral. Together, the minerals, cells, and fibres form an organic matrix or “osteoid”.
Bone is constantly undergoing bone formation by osteoblasts and bone resorption by osteoclasts. If blood calcium levels are lowered, resorption of the bone increases to fulfil calcium requirements elsewhere in the body.
Altered bone metabolism can be characterized by a misbalance between bone formation and bone resorption. It can occur in relation to several types of disorders. Examples are osteoporosis, osteopenia, Paget's disease, osteolytic metastasis in cancer patients, osteodistrophy in liver disease and the altered bone metabolism caused by renal failure or haemodialysis, bone fracture, bone surgery, aging, pregnancy, and malnutrition.
Bone loss is accelerated with aging. The major bone disease in the older population is osteoporosis. This disease is characterized by extensive bone loss leading to an increase in bone fragility and a greater risk of fractures. It causes considerable pain, disability, disfigurement and loss of independence, and is a cost and burden to health services. Internationally, more than 1.5 million fractures occur every year as a result of osteoporosis.
There are two types of osteoporosis recognized. The first typically occurs between the ages of 50 and 75 and affects six times as many women (post-menopausal osteoporosis) as men. The second type is referred to as senile osteoporosis and affects both men and women over 75 years of age and does not involve greater than normal bone loss. The risk factors for both types of osteoporosis are high caffeine intake, alcohol consumption, low body weight and low calcium intake.
The most prominent and well-documented cause of post-menopausal osteoporosis is estrogen deficiency. After the menopause, the ovaries cease to produce this hormone, which directly relates to loss of bone mineral content. A known treatment for post-menopausal symptoms, including osteoporosis, is hormone replacement therapy (HRT), and this estrogen replacement effectively prevents the development of osteoporosis. However the use of HRT may have serious side effects, e.g. breast tissue growth stimulation, and an alternative treatment for post-menopausal osteoporosis is required.
The main causes of other types of bone disorders have yet to be determined and a treatment for such disorders is required.
It is an aim of a preferred embodiment of the present invention to provide a method for the prevention or treatment of bone disorders and compositions for use in such methods.